Improve documentation

[devnote-dev]

I think it's safe to say that the majority of the library is undocumented or is lacking sufficient documentation. This isn't really useful if you're trying to implement a custom renderer which has many methods, or even make use of the parsers. Adding doc comments to the necessary classes/methods/etc would resolve this (maybe with examples too?), then possibly having the docs hosted? Of course, this isn't required, but it's definitely a plausible solution.